Novel camera sensors can capture scenes of much wider dynamic range than a standard display device can display. The result of this mismatch is that printed and displayed images are commonly lacking in clear detail. The problem is even more pronounced for synthetic images produced by fusing multiple views of a scene. Tone mapping operators are used to bridge this mismatch. They compress the dynamic range of a high dynamic range scene to the displayable range while reproducing as much as possible of the visual sensation of the scene.
Tone mapping operators can be classified according to whether their operators are spatially uniform or non-uniform. Spatially uniform operators, so called global operators, are independent of the local spatial context. They apply the same transformation function on each pixel of the image. Spatially non-uniform operators, so called local operators, use a transformation function that varies adaptively with the local characteristics of the image. In general, spatially non-uniform operators produce higher quality tone mapped images than spatially uniform operators, but they have some drawbacks. Visually, the main disadvantage of spatially non-uniform operators is the appearance of “halo” artifacts; these are dark or white bands that appear at the borders between regions of different brightness in the image. Spatially non-uniform operators require complex computations, and implementing them in real-time on an embedded system is a challenging task.
Accordingly, there is a need in the art for a method capable of real-time implementable local tone mapping of high dynamic range images.